linux-kernel - Re: [PATCH v14 072/113] KVM: TDX: handle vcpu migration over logical processor

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Date:   Wed, 12 Jul 2023 14:08:15 +0800
From:   "Wen, Qian" <qian.wen@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com
Subject: Re: [PATCH v14 072/113] KVM: TDX: handle vcpu migration over logical
 processor

On 5/29/2023 12:19 PM, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> For vcpu migration, in the case of VMX, VMCS is flushed on the source pcpu,
> and load it on the target pcpu.  There are corresponding TDX SEAMCALL APIs,
> call them on vcpu migration.  The logic is mostly same as VMX except the
> TDX SEAMCALLs are used.
> 
> When shutting down the machine, (VMX or TDX) vcpus needs to be shutdown on
> each pcpu.  Do the similar for TDX with TDX SEAMCALL APIs.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/kvm/vmx/main.c    |  32 ++++++-
>  arch/x86/kvm/vmx/tdx.c     | 168 +++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/tdx.h     |   2 +
>  arch/x86/kvm/vmx/x86_ops.h |   4 +
>  4 files changed, 203 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 17fb1515e56a..29ebd171dbe3 100644

...

> @@ -455,6 +606,19 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu)
>  		return;
>  	}
>  
> +	/*
> +	 * kvm_free_vcpus()
> +	 *   -> kvm_unload_vcpu_mmu()
> +	 *
> +	 * does vcpu_load() for every vcpu after they already disassociated
> +	 * from the per cpu list when tdx_vm_teardown(). So we need to
> +	 * disassociate them again, otherwise the freed vcpu data will be
> +	 * accessed when do list_{del,add}() on associated_tdvcpus list
> +	 * later.
> +	 */

Nit: kvm_free_vcpus() and tdx_vm_teardown() are typos? I don't find these functions.

> +	tdx_disassociate_vp_on_cpu(vcpu);
> +	WARN_ON_ONCE(vcpu->cpu != -1);
> +
>  	if (tdx->tdvpx_pa) {
>  		for (i = 0; i < tdx_info.nr_tdvpx_pages; i++) {
>  			if (tdx->tdvpx_pa[i])